Diesel engines mounted to vehicles such as dump trucks are generally provided with an exhaust gas processing apparatus such as an exhaust gas recirculation (EGR) apparatus, a diesel particulate filter (DPF) apparatus, or a catalyst reducing apparatus in order to purify exhaust gas. The EGR apparatuses mitigate NOx (nitrogen oxides) contained in exhaust gas by taking a part of the exhaust gas in an intake system again and causing combustion. The DPF apparatuses are filters for removing particulate matters (PMs) contained in exhaust gas. In the DPF apparatus, when the amount of sediment PMs exceeds a set value, the PMs are combusted for recycling. Catalyst reducing apparatuses convert NOx into nitrogen molecules and water by a catalyst.
In such an exhaust gas processing apparatus, the air volume sucked into a diesel engine is detected and each operation is controlled based on the detected intake air volume. For example, in the EGR apparatus, the flow rate of exhaust gas taken in an intake system is determined based on the intake air volume. In the DPF apparatus, a differential pressure between an upstream side and a downstream side is calculated from the intake air volume and the amount of sediment PMs is estimated from the calculated differential pressure. In the catalyst reducing apparatus, the amount of reducing agent supplied to a catalyst is optimized based on the intake air volume (e.g. see Patent Literature 1).